A sonde or fluid tight hollow body member for enclosing downhole well logging instrumentation is exposed to substantial shock. For instance, it is exposed to significant shock impact during transportation. When loaded on a logging truck bumps in the road (roads to oil well sites are notoriously poor) could create very high shock impact as the tool bounces unconstrained in its metal container. Moreover, a sonde lowered to the bottom of a well is typically retreived at relatively high speed as it pulled up through the well bore hole. It might be pulled at a rate of 120 feet per minute suspended on a logging cable as it is hoisted from the well. When it moves at this velocity and swings from side to side even slightly, it bangs against the surrounding casing or open hole and again experiences significant shock loading.
Another envirnmental hazard is encountered by downhole logging equipment lowered into a well borehole. This involves heat transfer primarily from the circuitry supported in the sonde which generates heat to the borehole. The amount of heat depends on the nature of the circuitry. In some instances, the amount of heat can be quite large, and the heat transfer rate required from the electronic components is substantial. Heat transfer can be improved by utilizing metallic supports to fasten the electronic components in the housing or sonde, but this inevitably couples vibration from the housing back to the electronics components. To the degree that the electronics are isolated from vibration, such isolation typically also provides thermal isolation and hence tends to concentrate heat at hot spots within the housing.
The present invention provides an apparatus which enables construction of a shock mounting in a logging sonde. The shock mounting isolates the electronic package so that the vibration experienced at the housing is not directly or fully coupled to the electronic components. On the other hand, the shock mount apparatus of the present invention provides an improved heat transfer rate. For this reason, the apparatus of the present invention enables simultaneous high quality shock or vibration isolation with good heat transfer for electronic packages in a downhole sonde.
Another important feature of this apparatus is the provision of a vibration isolation system which can be adapted to various sizes and shapes of components. That is, it can accommodate electronic component supports including circular wafers or lengthwise circuit boards. In all instances, the apparatus accommodates variations in shape and profile. Separately, the device is able to withstand vibrations substantially indefinitely because the possibility of metal fatique is nil.
The apparatus of the present invention may be summarized as an oval turn coil spring member placed in cooperative engagement with a shallow groove wherein the coil spring member is interposed between the outer sonde housing and an electronic support wafer. The device will be understood more readily upon a review and consideration of the description of the preferred embodiment below in conjunction with the drawings incorporated herewith.